The invention relates to an instrument for the surgical excision of a piece of tissue with a conical form and having an aperture, from a human or other animal body using a laser beam. Such an instrument may comprise a guide housing with a tube through which the incoming laser beam shines, an inlet deflecting member deflecting the laser beam out from its inlet direction, and an outlet deflecting member, offset laterally from the inlet deflecting member, for deflecting the laser beam along an outlet direction thereof so that on rotating the guide housing about the inlet path the emerging laser beam sweeps out a conical surface. The instrument is furthermore provided with a guide pin able to be plugged into the aperture for locating the guide housing during rotation.
The main parts of the human uterus are its body (corpus uteri) and its neck (cervix uteri). The neck of the uterus protrudes a few centimeters into the vagina. This lowermost section of the neck of the uterus is referred to as the external os uteri (portio). At the mouth of the womb there is histological transition between the uterine mucous membrane, which lines the entire uterine cavity, and integument tissue (squamous epithelium), which covers the part of the uterus protruding into the vagina. The transitional zone is termed the transformation zone, which is a regenerative section, in which cell differentiation takes place. Atypical cells are also derived from this regenerative section and after a certain latent period may start malignant growth. The areas, in which such cellular alterations take place, may usually be localized by special examination methods (colposcopy) of the cervix. If a timely diagnosis is made such preinvasive stages of carcinoma of the cervix uteri may be extirpated by the removal of a smaller or larger cone of tissue with a size dependent on the diagnosis made. Such an operation thus makes it possible to save the uterus, something that is extremely important for young patients in order to preserve fertility.
In order to perform this operation the German specification 2,309,205 has described an instrument of the initially mentioned type, which in use is introduced into the vagina so that its locating pin may be introduced into the os uteri. After switching on the laser the tube is rotated about the tube axis together with the inlet and outlet deflecting members so that the desired cone of tissue is cut out. As compared with conventional cutting using a knife, the method is substantially quicker and only lasts a few minutes. Furthermore the loss of blood is very small and there is hardly any postoperative hemorrhage. For this reason no secondary effects such as reduced fertility are likely. Furthermore the operation may be performed without hospitalization and the complication rate is negligible, while on the other hand conventional surgical methods involve a period in a hospital lasting about 8 days. A further advantage of such laser conization is that the extirpated cone may be readily examined pathologically after the operation.
However along with these advantages conization by a laser using the known instrument involves the following disadvantages:
The tube containing the deflecting parts in the form of mirrors is for its part borne in a stationary external tube. This design has to be radially symmetrical and thus takes up much space around it in the zone where the operation is being performed so that the site of the operation may only be observed using a microscope through the tube. In this respect only the actual point of cutting of the laser beam may be observed since the microscope light is deflected via the same mirrors to the site of the operation. Furthermore, owing to the lack of space available, the access of instruments to the site of the operation is limited.
A further shortcoming is to be seen in the fixed arrangement of the locating pin on the guide housing so that there is friction between the locating pin, which is entrained in rotation during the cutting out of the cone of tissue, and the tissue surrounding it so that the cone of tissue is subjected to torsion. This may mean that the conical form is imperfect and the cone of tissue may be torn out shortly before the end of the cutting operation. Furthermore the forces produced the centering of the locating pin may also be imperfect and this has an undesired effect on the resulting conical form.
This disadvantage is more likely prone to occur when the instrument is only held in the hand and is not held using a stationarily arranged external tube (so that in this case the external tube would perform the locating function).